Require const blocks to only use const stable things

Author: oli-obk

compiler/rustc_ast_lowering/src/asm.rs

@@ -197,7 +197,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         }
                     }
                     InlineAsmOperand::Const { anon_const } => hir::InlineAsmOperand::Const {
-                        anon_const: self.lower_const_block(anon_const),
+                        anon_const: self.lower_const_block(anon_const, &[]),
                     },
                     InlineAsmOperand::Sym { sym } => {
                         let static_def_id = self

compiler/rustc_ast_lowering/src/expr.rs

@@ -103,7 +103,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
             let kind = match &e.kind {
                 ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
-                ExprKind::ConstBlock(c) => hir::ExprKind::ConstBlock(self.lower_const_block(c)),
+                ExprKind::ConstBlock(c) => hir::ExprKind::ConstBlock(self.lower_const_block(c, attrs)),
                 ExprKind::Repeat(expr, count) => {
                     let expr = self.lower_expr(expr);
                     let count = self.lower_array_length_to_const_arg(count);
@@ -386,12 +386,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
         })
     }
 
-    pub(crate) fn lower_const_block(&mut self, c: &AnonConst) -> hir::ConstBlock {
+    pub(crate) fn lower_const_block(&mut self, c: &AnonConst, attrs: &'hir [hir::Attribute]) -> hir::ConstBlock {
         self.with_new_scopes(c.value.span, |this| {
             let def_id = this.local_def_id(c.id);
+            let hir_id = this.lower_node_id(c.id);
+            if !attrs.is_empty() {
+                this.attrs.insert(hir_id.local_id, attrs);
+            }
             hir::ConstBlock {
                 def_id,
-                hir_id: this.lower_node_id(c.id),
+                hir_id,
                 body: this.lower_const_body(c.value.span, Some(&c.value)),
             }
         })

compiler/rustc_ast_lowering/src/pat.rs

@@ -399,7 +399,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             ExprKind::Lit(lit) => {
                 hir::PatExprKind::Lit { lit: self.lower_lit(lit, span), negated: false }
             }
-            ExprKind::ConstBlock(c) => hir::PatExprKind::ConstBlock(self.lower_const_block(c)),
+            ExprKind::ConstBlock(c) => hir::PatExprKind::ConstBlock(self.lower_const_block(c, &[])),
             ExprKind::IncludedBytes(byte_sym) => hir::PatExprKind::Lit {
                 lit: respan(span, LitKind::ByteStr(*byte_sym, StrStyle::Cooked)),
                 negated: false,

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -255,6 +255,7 @@ impl<S: Stage> AttributeParser<S> for ConstStabilityParser {
         Allow(Target::AssocConst),
         Allow(Target::Trait),
         Allow(Target::Static),
+        Allow(Target::Expression), // FIXME: we really only want to allow inline consts
         Allow(Target::Crate),
     ]);
 

compiler/rustc_const_eval/src/check_consts/mod.rs

@@ -54,9 +54,11 @@ impl<'mir, 'tcx> ConstCx<'mir, 'tcx> {
     pub fn enforce_recursive_const_stability(&self) -> bool {
         // We can skip this if neither `staged_api` nor `-Zforce-unstable-if-unmarked` are enabled,
         // since in such crates `lookup_const_stability` will always be `None`.
-        self.const_kind == Some(hir::ConstContext::ConstFn)
-            && (self.tcx.features().staged_api()
-                || self.tcx.sess.opts.unstable_opts.force_unstable_if_unmarked)
+        matches!(
+            self.const_kind,
+            Some(hir::ConstContext::ConstFn | hir::ConstContext::Const { inline: true })
+        ) && (self.tcx.features().staged_api()
+            || self.tcx.sess.opts.unstable_opts.force_unstable_if_unmarked)
             && is_fn_or_trait_safe_to_expose_on_stable(self.tcx, self.def_id().to_def_id())
     }
 

library/core/src/intrinsics/mod.rs

@@ -2629,6 +2629,7 @@ pub const fn overflow_checks() -> bool {
 #[rustc_nounwind]
 #[rustc_intrinsic]
 #[miri::intrinsic_fallback_is_spec]
+#[rustc_intrinsic_const_stable_indirect]
 pub const unsafe fn const_allocate(_size: usize, _align: usize) -> *mut u8 {
     // const eval overrides this function, but runtime code for now just returns null pointers.
     // See <https://github.com/rust-lang/rust/issues/93935>.
@@ -2658,6 +2659,7 @@ pub const unsafe fn const_deallocate(_ptr: *mut u8, _size: usize, _align: usize)
 #[rustc_nounwind]
 #[rustc_intrinsic]
 #[miri::intrinsic_fallback_is_spec]
+#[rustc_intrinsic_const_stable_indirect]
 pub const unsafe fn const_make_global(ptr: *mut u8) -> *const u8 {
     // const eval overrides this function; at runtime, it is a NOP.
     ptr
@@ -2823,6 +2825,7 @@ pub const fn offset_of<T: PointeeSized>(variant: u32, field: u32) -> usize;
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_intrinsic]
+#[rustc_intrinsic_const_stable_indirect]
 pub const fn variant_count<T>() -> usize;
 
 /// The size of the referenced value in bytes.
@@ -2862,6 +2865,7 @@ pub const unsafe fn align_of_val<T: ?Sized>(ptr: *const T) -> usize;
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_intrinsic]
+#[rustc_intrinsic_const_stable_indirect]
 pub const fn type_name<T: ?Sized>() -> &'static str;
 
 /// Gets an identifier which is globally unique to the specified type. This
@@ -2877,6 +2881,7 @@ pub const fn type_name<T: ?Sized>() -> &'static str;
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_intrinsic]
+#[rustc_intrinsic_const_stable_indirect]
 pub const fn type_id<T: ?Sized + 'static>() -> crate::any::TypeId;
 
 /// Tests (at compile-time) if two [`crate::any::TypeId`] instances identify the

tests/ui/consts/min_const_fn/const-fn-lang-feature.rs

@@ -16,5 +16,8 @@ const fn my_fun2() {
 }
 
 fn main() {
-    const { my_fun2() };
+    #[rustc_const_unstable(feature = "abi_unadjusted", issue = "42")]
+    const {
+        my_fun2()
+    };
 }